Vogt J A, Yarmush D M, Yu Y M, Zupke C, Fischman A J, Tompkins R G, Burke J F
Universitätsklinikum für Anaesthesiogie, Universität Ulm, Germany.
Am J Physiol. 1997 Jun;272(6 Pt 1):C2049-62. doi: 10.1152/ajpcell.1997.272.6.C2049.
Infusion of 13C-labeled lactate into rabbits and the subsequent measurement of glutamate isotopomers by 13C nuclear magnetic resonance (NMR) spectroscopy enables one to calculate relative flow rates associated with the tricarboxylic acid (TCA) cycle, albeit with a lower precision than one would obtain using a perfused organ. Two factors contribute to the lower precision in the determination of relative flow rates for the in vivo system: 1) a poorly defined pyruvate input and 2) low levels of 13C-enriched oxaloacetate and acetyl-CoA isotopomers, which give rise to weaker glutamate isotopomer NMR signals. To help overcome these limitations, we introduce a procedure to 1) include experimental data from gas chromatography-mass spectrometry (GC-MS) and 2) account for the uncertainty in the labeling of the input to pyruvate by creating the labeling as a measurement that is subject to measurement error. The effects of the uncertainties in the input labeling, NMR data, and MS data are evaluated via a Monte Carlo method. The change in the precision of the relative fluxes for the cases of high/low NMR and high/low MS precision is given. An uncertainty in the lactate measurements of up to 10% does not add significantly to the imprecision of the relative flow rates.
向兔子体内输注13C标记的乳酸盐，随后通过13C核磁共振（NMR）光谱法测量谷氨酸异构体，这使得人们能够计算与三羧酸（TCA）循环相关的相对流速，尽管其精度低于使用灌注器官所获得的精度。有两个因素导致体内系统相对流速测定的精度较低：1）丙酮酸输入定义不明确；2）13C富集的草酰乙酸和乙酰辅酶A异构体水平较低，这导致谷氨酸异构体NMR信号较弱。为了帮助克服这些限制，我们引入了一种方法，1）纳入气相色谱-质谱（GC-MS）的实验数据，2）通过将标记视为受测量误差影响的测量值，来考虑丙酮酸输入标记中的不确定性。通过蒙特卡罗方法评估输入标记、NMR数据和MS数据中的不确定性影响。给出了高/低NMR精度和高/低MS精度情况下相对通量精度的变化。乳酸盐测量中高达10%的不确定性不会显著增加相对流速的不精确性。
